Heme rescues a two-component system Leptospira biflexa mutant

Unité de Biologie des Spirochètes, Institut Pasteur, Paris, France.
BMC Microbiology (Impact Factor: 2.73). 02/2008; 8(1):25. DOI: 10.1186/1471-2180-8-25
Source: PubMed


Heme is typically a major iron source for bacteria, but little is known about how bacteria of the Leptospira genus, composed of both saprophytic and pathogenic species, access heme.
In this study, we analysed a two-component system of the saprophyte Leptospira biflexa. In vitro phosphorylation and site-directed mutagenesis assays showed that Hklep is a histidine kinase which, after autophosphorylation of a conserved histidine, transfers the phosphate to an essential aspartate of the response regulator Rrlep. Hklep/Rrlep two-component system mutants were generated in L. biflexa. The mutants could only grow in medium supplemented with hemin or delta-aminolevulinic acid (ALA). In the pathogen L. interrogans, the hklep and rrlep orthologous genes are located between hemE and hemL genes, which encode proteins involved in heme biosynthesis. The L. biflexa hklep mutant could be complemented with a replicative plasmid harbouring the L. interrogans orthologous gene, suggesting that these two-component systems are functionally similar. By real-time quantitative reverse transcription-PCR, we also observed that this two-component system might influence the expression of heme biosynthetic genes.
These findings demonstrate that the Hklep/Rrlep regulatory system is critical for the in vitro growth of L. biflexa, and suggest that this two-component system is involved in a complex mechanism that regulates the heme biosynthetic pathway.

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Available from: Jean-Michel Betton
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    • "Different genes with the same predicted function, such as putative metallopeptidases (LIC11149 and LIC10271), sensor or receiver proteins of two-component response regulators (LIC20012, LIC11201, LIC12807, LIC12979 and LIC13289), and adenylate/guanylate cyclase (LIC10900 and LIC11095) were found to be regulated in opposite directions. LIC20012, an ortholog of hklep encoding a sensor kinase of the Hklep/Rrlep two-component system involved in heme biosynthesis in L. biflexa [54], was down-regulated. However, an ortholog of rrlep regulator (LIC20013) was not differentially expressed. "
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